Archive for the system card bios bugs/quirks Category

System card bios bug

Posted in hacks, Megaman, NES2PCE, system card bios bugs/quirks on January 21, 2014 by pcedev

I’m working on the title screen and options menu for the Megaman CD release. I came across a bug in the load graphic data for the IPL configuration – thingy. The Hu7 doc mentions that 1 record is used for PAL data and 1 record is used for BAT data, with the rest of the records used for actual vram data. But there’s a bug in the PAL record handling. It reads the record and writes all 256 color entries to the BG,  but when it writes to the SPR area – it only increments the pointer by 0x100 bytes; not the required 0x200 bytes. While you can still use this to have it load BG and SPR PAL data, it will only load 128 colors for each if you treat it as such. I.e. 256 colors gets transferred to BG PAL ram, but the last 128 colors of that 256 color block gets written to SPR PAL ram.